Reactors, having the configuration of containers with stirrers, are known. However, the ratio of the surface area to the volume of the product is poor in such reactors. Only a limited build up of intrinsic viscosity is possible here. Moreover, for this type of reactor, a high input of energy is required. The configuration of the heating system is expensive in this case, the surface area, required for degassing the product, being produced only inadequately by the stirrer. There is no possibility of subsequently expanding the reaction space in order to increase the output of the reactor and, accordingly, to raise the capacity of the installation and/or of the production.
The use of containers with special stirring mechanisms also proves to be disadvantageous. The manipulation of the product, required for producing the necessary reaction surface area, is complicated from a production engineering point of view and the special construction, resulting therefrom, is expensive. The stirring mechanism, additionally used for producing the highest possible surface area, has the disadvantages described above. For these reactors also, a high energy input is necessary. The configuration of the heating proves to be very expensive.
The DE 10155419 A1 discloses a “Method for the continuous production of high molecular weight polyester as well as a device for carrying out the method”. The reaction and the production of surface area take place in the tower reactor described by means of a falling film evaporator.
The use of a falling film evaporator represents a difficulty in case of a breakdown, since the pipes of the falling film evaporator may become blocked with thermally degraded material. Moreover, a tower reactor is a complicated and, with that, an economically expensive construction.
The U.S. Pat. No. 5,310,955 A discloses a vertical reactor system, in which the reaction mixture passes from the top to the bottom through different cylindrical compartments and mixing is accomplished by a stirring mechanism. The sealing of the individual compartments, which are connected by the shaft of the stirring mechanism, turns out to be difficult. On the one side, mixing of the reaction material is improved by the stirring mechanism itself. However, the reactive surface area is increased only to a very limited extent. The unfavorable diameter to height ratio of the individual compartments also comes to bear here.
The U.S. Pat. No. 4,289,895 (DE 2504258) discloses a method for producing oligomeric alkene terephthalates. A device is described here, in which the reaction takes place in several stirred cylindrical chambers, which are disposed on top of one another and some of which are stirred. Moreover, each chamber has a separate heating system. In the upper part, the reaction takes place under pressure, whereas, in the lower part, a vacuum is applied.
For this device also, there is an unfavorable ratio of diameter to height in the vacuum area, the reactive surface area generated being small in relation to the capacity. The stirring mechanisms are also concerned only with thorough mixing and not with producing the required reactive surface area. The individual heating systems for each chamber make the device very expensive.
Horizontal reactors are equipped with a cumbersome stirring mechanism for generating surface area. In the course of time, the mechanical stresses on the seal, which develop at the shaft ducts, result in leaks, which may lead to the entry of oxygen from the air into the reaction space, which is harmful for the product.